1. Field of the Invention
The invention relates generally to the field of excavating of wellbores. More specifically, the present invention relates to an apparatus and method for inducing fluid circulation over an excavation bit. Yet more specifically, the present invention further relates to inducing fluid circulation over a circulation bit during side bore excavating.
2. Description of Related Art
In excavating or operations within a wellbore 5, drill bits are often used in the drilling or coring of a wellbore 5 that extends from the earth's surface into and through a subterranean formation 8. The drilling involved includes the drilling of a standard vertical wellbore 5, slanted or deviated wellbores (not shown), as well as lateral wellbores 6 that extend at a substantially perpendicular direction from a primary wellbore 5. These are standard drilling operations and they involve circulation of drilling fluid through a drill string (or drill pipe) from the surface above the wellbore 5.
Generally, when forming lateral wellbores 6 a coring tool 10 may be used as shown in FIG. 1. Coring tools 10 are deployed in a wellbore generally on a logging cable and in some cases on tubing or drill pipe, but even then fluid circulation from the surface to the coring tool 10 is not possible. The coring tools 10 comprise means for urging a coring bit 26 against the inner wall of a wellbore 5 for drilling a lateral wellbore 6—where the coring bit 26 is disposed on the end of a drill shaft 23. A driver 20 can be attached to the coring drill 22 as a drive source to the drill shaft 23 thereby providing a rotational force to the coring bit 26 for drilling into the formation 8 around the wellbore 5. The driver 20 can be powered by hydraulic fluid provided within a hydraulic feed line 18, or other mechanical means. Push rods 12, working in combination with associated piston heads 14 disposed within a cylinder 16 can provide the lateral force necessary for urging the coring drill 22 into the formation 8.
During most vertical excavating operations a fluid is generally supplied to the drill bit for cooling and lubricating the drill bit and to wash away debris accumulated during excavating within a wellbore. Once the fluid passes through the cutting zone it generally flows to the surface for treatment where it can be filtered and possibly refurbished. As is well known, the fluid supplied to the bit is typically a drilling fluid that is supplied under high pressure. The drilling fluid must be supplied at high pressure to overcome the local high pressure within the wellbore as well as to have sufficient velocity for removing the debris away from the bit. This debris, which includes shards of rock and other material cut from the formation, as well as broken pieces of the drill bit or coring device, remains between the face of the drill bit and the formation and can greatly hinder the ability of further excavating through the formation.
Ports and fluid nozzles (not shown) generally are provided at the drill bit for directing the drilling fluid for directing the drilling fluid from the drill bit into the cutting zone. Various drilling fluid flow paths are utilized depending on the composition of the earth formation being drilled. Most drill bits include downwardly directed nozzles for flushing and removing the formation cuttings from the bottom of the well hole. Some drill bits include nozzles that direct drilling fluid on the cutting elements to prevent clogging of the cutting elements in earth formations.
While fluids have been successfully implemented in typical vertical drilling operations, when coring operations are performed, fluids have not been supplied to the face of the drill bit of a coring drill 22. Accordingly, in the absence of a cleaning and lubricating fluid, coring operations are often severely hindered by an accumulation of formation shards and other debris collecting at the face of the coring drill 22. Therefore a need exists for a device and method of providing fluids to the bit of a coring drill 22 during use.
Pumps (not shown) are used in pressurizing the drilling fluid and delivering the pressurized fluid to the drill bit. The pressurized fluid can flow from the pump discharge to the bit through a drill string or other tubular member. When the coring tool 10 is lowered on a cable or wireline, it is technologically extremely complicated and economically not feasible to create fluid circulation involving pumps as part of the tool. Therefore, a true advantage over prior art devices exists in an apparatus capable of inducing fluid flow in the cutting zone that exists between a drill bit and the subterranean formation where excavation is being conducted.